For example, for the light source device included in the projection-type display device such as a projector, a lamp including a bulb that generates light by electric discharging may be used. The light source device of this type may have a structure for cooling the bulb because the bulb generates heat during the use of the lamp.
In the bulb, there is arranged a pair of electrodes that discharges electricity to generate light. When the pair of electrodes face each other with an angle in a vertical direction, for an electric arc that is a basic point to generate light by electric discharging, a convex arc is known to be drawn on a side opposite the force of gravity. In this case, the temperature of the bulb is higher on the upper side than on the lower side in the vertical direction. To maintain the life of the bulb, it is particularly advisable to keep the temperature of the bulb within a desired range, and improvement of the cooling accuracy of the bulb is important. Unless the temperature of the bulb is kept within the desired range, clouding or blackening may occur to shorten the life of the bulb, consequently causing luminance reduction or emission abnormality such as flickering.
When the entire bulb is uniformly cooled, a temperature difference of about 100 to 150° C. may be generated between the upper side and the lower side of the bulb in the vertical direction. Thus, when the upper side of the bulb in the vertical direction is cooled to an optimal temperature, the lower side of the bulb in the vertical direction is excessively cooled. When the lower side of the bulb in the vertical direction is cooled to an optimal temperature, the upper side of the bulb in the vertical direction is insufficiently cooled.
The light source device such as the projector may be located above an installation surface (floor installation) or below the installation surface (suspension installation). In such a light source device, in both cases of the floor installation and the suspension installation, it is advisable to efficiently cool the upper side of the bulb in the vertical direction.
JP2002-298639A (hereinafter, referred to as Patent Literature 1) and JP2006-243635A (hereinafter, referred to as Patent Literature 2) disclose light source devices that can cool the upper sides of the bulbs more intensively than the lower sides even when upside down.
The light source devices described in Patent Literature 1 and Patent Literature 2 include ducts for guiding cooling air to cool the bulbs. A wind direction control plate is disposed in the duct. The wind direction control plate changes the direction of the cooling air to cool the bulb. Accordingly, even when the light source device is upside down, the strong cooling air can be supplied to the upper side of the bulb in the vertical direction.
In the light source device described in Patent Literature 1, the cooling air out of the duct is jetted out in a direction having an angle with respect to the inner surface of the reflector, and bent toward the bulb in the inner surface of the reflector. The cooling air is dispersed when its traveling direction is curved. As a result, the cooling efficiency of the bulb may be reduced.
In the light source device described in Patent Literature 2, a cooling air guide is disposed in the jetting-out port of the duct. By this cooling air duct, the traveling direction of the cooling air jetted out from the duct is bent toward the bulb by about 90°. As a result, since the traveling direction of gas jetted out from the duct is greatly bent, the flow of gas may be dispersed to cause a reduction of cooling efficiency.
In particular, when the flow of gas to cool the upper side of the bulb in the vertical direction is dispersed to cause reduction of the cooling efficiency, the temperature of the upper side of the bulb may become excessively high.
In the light source device described in Patent Literature 2, the duct for guiding the cooling air is bent by about 90° near the inlet. When this structure becomes complex, a problem of the enlarged duct may occur.